MARTIN LISTER’S 1678 <em>AMMONIS CORNU</em> AND THE MISREADING OF <em>HILDOCERAS BIFRONS</em> (BRUGUIÈRE, 1789). AN HISTORICAL INSIGHT ON THE RELEVANCE OF ARTWORK AND DETAILS IN TAXONOMY

Hildoceras bifrons (Bruguière, 1789) is a cosmopolite ammonite species from the Lower Jurassic of Boreal and Mediterranean (Tethys) palaeogeographical provinces. Inter-demic phylogenetic variability are noticeable, also affecting most distinctive morphological trait: spiral groove along whorl flank. Since XIX century, however, number morphotypes assigned to (many which Apennines other Italian localities) lacked neat groove, replaced by shallow, variably evident discontinuous inflection. Buckman (1918) provided photographic illustration specimen he interpreted as corresponding holotype, until then represented drawing described Lister (1678) Ammonis cornu. Buckman’s assessed well-carved feature holotype trademark species. Nevertheless, several authors insisted on referring faintly grooved specimens bifrons, an attitude thus envisaged due their negligence or inaccuracy. In contrast with this view, it herein argued that, one hand, illustrated Buckman, in quality neotype, differs Lister’s point that may not be same specimen; (never formally invalidated holotype) could have been legitimately considered representative those now lusitanicum Meister, 1913. This alternative view clarifies taxonomic approach held many authors, proving coherency work rather than at superficial evaluation diagnostic traits.